Dichloromalonaldehydates



Patented Nov. 13, 1951 Croxall, Bryn Athyn, Pa., assignors to Rohm & H as C m ny adelphia, Be-, or

ration of Delaware No Drawing. Application August 19, I949, Serial No. 111,33&

4 Claims. (01. 2605-483) 1 This invention deals with alkyl dichloromalonaldehydates,

wherein R is an alkyl group of not over four a carbon atoms; It provides a methodbywhich these compounds may be prepared from. alkyl ,s alkoxyacrylates.

The alkyl pealkoxyacrylates' are available through the reaction of acetylene on dialky-l; carbonates in the presence of an anhydrous strongly basic catalyst. This reaction is fully described in application, Serial No. 52,607, filed October 2-, 1948 (now Pat. No. 2,535,012) by Croxalland Schneider. Acetylene is run into an alkyl care bonate at to 110 C. in the presence ofa catalyst, the catalyst is destroyed, and the "re, action products which include alkyl fi-alkoxyacrylates and alkyl 5, ,s-dialkoxypropionates are separated. Typical carbonates are dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, die isobutyl carbonate, and sec.butyl carbonate. Typical catalysts are alkali metal acetylides,-in eluding sodium acetylide, potassium aeetylide, or disodium acetyli'de, alkali metal alcoholates, including sodium methylate, ethylate, orbutoxide, and quaternary ammonium alkoxides, such as benzyl trimethyl ammonium methoxida. dibenzyl dimethyl ammoniumethoxide, or benzyl trimethyl ammonium tert.-butoxide.

From the reaction mixture theresareobtained non-tertiary alkyl as-dialkoiqzpropionates, "alk-y-l B-alkoxyacrylates, dialkyl dialkoxysuccinates, and dialkyl alkoxymaleates. The first two are readily collected in one fraction and whilethey may then be separated, this step is not essential. The alkyl ap-dialkoxypropionates, whether-alone or in admixture with alkoxy'acrylate, are con verted to correspondingo-alkoxyacrylates when heatedwith a dealcoholating catalyst, and one mole of alcohol is taken olT per mole Off'di'" alkoxypropionate. This process is more fully described in application, Serial No. 52,608yfi1ejd by Croxall and Schneider on October 2, 1948;, now Pat. No. 2,571,212,. This process makes readily available methyl p-methoxyacrylate, ethyl p-ethoxyacrylate, propyl p-propoxyacrylate, or butyl fi-butoxyacrylate, and the like.

The reaction between any one of these or an e uiv lent al yl fielkq ac y ate a hyp ch orous acid solution s, carri d ut elowlZO. C. and preferably between 0, and,10, Q. The, hyp hl o s acid is es us d n aqueous so ution at a Concentration from one per cent to five per cent, although both weaker and somewhat stronger solutions may be used. Hypochlorous acid solution is, added in excess and the resulting reaction product is then separated.

A-convenient method for effecting the isolation of the alkyl dichloromalonaldehydate is through salting out and separation of brine and organic layer. The organic layer may be purified by distillation.

To illustrate. the various procedural steps which have bee described, there will now be given examples which are. typical of practical methods finally yieldingthe alkyl a,a-dichloromalonaldehydates or this invention.

AQPREPARATION OF DIETHER PRO- PIONATES AND E'IHER ACRYLATES Eagample 1 In an apparatus having a gas-tight, stainlesssteel stirrer, there was placed 225 grams oranhydrous ethyl alcohol. Small cubes of sodium were gradually added thereto in an amount of S O'gramS. The sodium was dissolved with the formation of sodium ethylate. Excess alcohol was distilled off under reduced pressure. To the sodium ethylate there were added 2200 grams of diethyl carbonate. The reaction vessel was then equipped with gas inlet and outlet tubes, manometer, and thermometer. It was flushed with nitrogen and heated to 80" C. Acetylene was passed in until the rate of absorption be came very slow. The vessel and contents were cooled and the flow of acetylene discontinued. Dilute acetic acid was added to destroy the catalyst. Two layers formed. The upper oily layer was separated and f-ractionally distilled.

- A i'orerun taken at atmospheric pressure consistedorethyl alcohol and ethyl carbonate. Distillationwas continued under reduced pressure. A fraction distilling at -75 C'./2-4 mm. consisted o'f'10% of ethyl fl-ethoxyacrylate and 90%. of ethyl fifi-diethoxypropionate. At C./4 mm, a fraction, of pure ethyl pfi-diethoxyproe pionatewasobtai-ned. Between 75 C./4' mm. and 114" C./-3mm., a mixture of ethyl p,s-di-. ethoxypropionate and diethyl a,a-diethoxysuc,- cinate was take off. At. 114-115 C./34 mm., there was. obtained a fraction consisting of diethyl -.diethoxysuccinate. .On further distillation, a. traction containing this other succinate and d hyl wet oxymaleate was obt n d- In the same way other esters of carbonic acid and monohydric alcohols may be reacted with as above. Other alkaline catalysts may be used B. CONVERSION OF ALKYL sp-DLALKOXY PROPIONATES TO ALKYL B-ALKOXY- ACRYLATES v Example 2 A mixture of 192 grams of ethyl pfi-dithoxypropionate and one gram of sodium acid sulfate was placed in a reaction vessel equipped with a short packed column and slowly heated. At about 80 0., there began to be evolved vapors of ethyl alcohol. Heating was continued with distillation of the alcohol. Pot temperatures advanced to 150 C. with the overhead temperatures of 785 C. to 80 C. A total of' 44.5 grams of ethyl alcohol was taken off. Heating was continued and at 85.5-86.5 C./ 19 mm., a main fraction was taken which was ethyl p-ethoxyacrylate.

Example 3 In accordance with the method of Example 2, a mixture of 96 grams of n-butyl p,,8-di(n-butoxy)propionate and 0.25 gram of sodium acid sulfate was heated. At batch temperatures of 110-160 C., there was evolved n-butanol with overhead temperatures of 110 to 114 C. The batch temperature was carried to 180 C. At 110-111 C./3 mm, there was obtained the main fraction which consisted of butyl B-butoxyacrylate.

Example 4 C. REACTION OF ALKYL B-ALKOXYACRY- LA'I'ES AND HYPOCHLOROUS ACID Example 5 In a reaction vessel equipped with stirrer, thermometer, dropping funnel, and reflux condenser was placed 58 parts by weight of methyl B-methoxyacrylate. This material was stirred and cooled by means of an ice bath. A freshly prepared 5% hypochlorous acid solution was slowly run into the reaction vessel until a definite excess was present. This state was tested for by removal of a small sample of solution and addition of an acidified potassium iodide solution to it. With an excess of hypochlorous acid present, stirring was continued for a half hour.

Sodium chloride was then added to the reaction mixture. An oil separated and was taken off. It was dried over sodium sulfate and distilled. A fraction which corresponded to methyl c m-dichloromalonaldehydate was taken off at '70-'-75 C /3o mm.

Example 6 A charge of 72 parts by weight of ethyl p-ethoxyacrylatewas placed in the reaction vessel and chilled to 0 C. A five per cent hypochlorous acid solution was slowly added until 2000 parts had been used. Stirring was continued for 15 minutes and the product was then salted out. It was collected as an oil, dried over sodium sulfate, and

' distilled. At 79-80 C./19 mm., a fraction of 31 7 parts was collected. It corresponded in composition to ethyl a,a-dichloromalonaldehydate. It had a refractive index, 11. of 1.4460, a density of 1.324, and a, saponification number of 625 (theory 605).

Example 7 In the same way 50 parts of butyl p-butoxyacrylate was reacted at 0-15 C. with hypochlorous acid in about a 5% aqueous solution, about 1000 parts of this solution being necessary. The reaction product was separated as an oil and purified by distillation at l15123 C./30 mm. It corresponded in composition to that of butyl a,adlchloromalonaldehydate.

As an alternative method for preparing the alkyl dichloromalonaldehydates, the alkyl fi-alkoxyacrylates are converted to alkyl a-chloro-palkoxyacrylates which are then reacted with hypochlorous acid. The alkyl a-chloro-fl-alkoxyacrylates are prepared by the method described in our Application Serial No. 111,331, filed on even date, now U. S. Patent 2,526,007, issued October 1'7, 1950.' Chlorine is run into an alkyl ,9- alkoxyacrylate at -5 C. to 20 C. to form an addition product which is then heated with resulting dehydrochlorination to yield the desired alkyl a-chloro-li-alkoxyacrylate.

Typical examples of this preparation follow.

Example 8 (a) There were mixed in a reaction vessel equipped with stirrer, reflux condenser, and gas inlet tube 216 parts by weight of ethyl fl-ethoxyacrylate and 200 parts of chloroform. This mixture was cooled by use of a salted ice bath. Chlorine gas was bubbled through the mixture while it was kept below 10 C. When an excess of chlorine had been added as shown by development of a yellow color, the passage of chlorine was discontinued. Excess chlorine and part of the chloroform were removed under reduced pressure while the reaction mixture was gently warmed, The product was ethyl afi-diChIOlO-B-EthOXYDI'O- pionate in chloroform solution.

(b) A mixture of 178.5 parts of ethyl fi-ethoxyacrylate and 250 parts of chloroform was reacted with chlorine as in (a) above. Excess chlorine and chloroform were taken off by heating. Hydrogen chloride was evolved and the material in the reaction vessel was heated to 150-160 C. for two hours. It was then fractionally distilled. A forerun of a small amount of ethyl p-ethoxyacrylate was obtained at -150 C./61 mm. 1 At -155 C./61 mm., there was distilled ethyl a: chloro-fi-ethoxyacrylate. It has a refractive index, n of 1.4728. By analysis the product obtained contained 20.11% of chlorine. The theoretical chlorine content for ethyl-a-chloro-sethoxyacrylate is 19.85%. The yield was 92%.

Example 9 vEthyl a,,8-dichloro-fl-ethoxypropionate was prepared as in Example 8 (a) above. It was run very slowly, into a mixture of 1.35 gram moles of triethylamine in 400 ml. of ethyl ether until 1.28

gram moles of the ether ester had been added. Triethylamine hydrochloride was formed and was separated by filtration. The ether wasdistilled oil? and the resulting material filtered to remove additional triethylamine hydrochloride which had separated. It was then distilled at 78-80 C./l mm. to give a 78% yield of ethyl a-ChlOlO-B- ethoxyacrylate.

Example (a) A solution of 116 parts by weight of methyl fi-methoxyacrylate in 250 parts of chloroform was cooled to 10 C. and treated with chlorine gas as in Example 8 (a). The temperature of the reaction mixture was kept between 2 and 10 C. by use of an ice-salt bath. As soon as a yellow color developed, excess chlorine was taken 01f along with most of the chloroform by stripping under reduced pressure. The product thus obtained was methyl a, 8-dichloro-p-methoxypropionate.

(b) A portion of this product was heated at 170 C. for 1.5 hours. Hydrogen chloride was taken off as it was evolved. The heated product was then fractionally distilled. A forerun of methyl p-methoxyacrylate was taken off at 95- 124 C'./28 mm. At 124-128 C./28 mm., a fraction was distilled which corresponded in composition to that of methyl a-chloro-B-methoxyacry late. The redistilled product boiled at 124-125 C./28 mm. and had a refractive index, 11 of 1.4838.

Example 11 (a) A mixture of 31.5 parts of butyl ,B-butoxyacrylate in 75 parts of chloroform was cooled to 5 C. and chlorine passed therethrough while the temperature was kept between 0 and 8 C. by

means of an ice-salt bath. The chloroform was distilled from the reaction mixture and the resulting material heated at 160-180 C. for an hour. It was then distilled at low pressure. After a forerun of butyl p-butoxyacrylate, there was obtained a fraction of 18 parts which distilled at 135-146 C./4 mm. and corresponded in composition to butyl a-chloro-fi-butoxyacrylate.

(b) A mixture of 89 parts of ethyl a-ChlOIO-flethoxyacrylate, 112 parts of normal butyl alcohol, and 2 parts of p-toluene sulfonic acid was heated in a reaction vessel equipped with a packed distilling column topped with partial take-01f head.

Ethanol was distilled from the reaction mixture.

When it was no longer obtained, the temperature was raised and butanol was taken off. The mixture was then subjected to fractional distillation at reduced pressure. A forerun of eight parts distilling at 90-122 C./4 mm. consisted of mixed ethyl a-chloro-B-ethoxyacrylate and butyl a-chloro-fi-butaxyacrylate. At 122-145 C./4 mm., there was obtained butyl a-chloro-fl-butoxyacrylate in an amount of 65 parts. This material was redistilled at 142-144 C./4 mm. to give a very pure product, which had a refractive index of 1.4674 and which contained by analysis 14.75% of chlorine (theory 14.76%).

The above example shows how the ether acrylates can be transetherified and transesterified as a means of passing from a lower ester to a higher. It should also be mentioned that by use of a mild dealcoholating catalyst, such as sodium acid sulfate, a smaller ether group may be replaced with a larger one without changing the ester group. Thus, ethyl fi-ethoxyacrylate is heated with butyl alcohol to yield ethyl p-butoxyacrylate or with octyl alcohol to yield ethyl p-octoxyacrylate. As shown above, the a-chloro-,6-alkoxyacrylates similarly undergo ether and ester interchange. The same reactions can be effected with the p-chloroa-alkoxymaleates.

The compounds thus prepared have the general formula ROCH=CC1COOR These are reacted with hypochlorous acid in the same way as the alkyl s-alkoxyacrylates and the same end products obtained. The following example is suincient to illustrate this method.

Example 12 To 65 parts by weight of ethyl a-OhlOlO-fiethoxyacrylate, cooled to 0-5 0., there was added with stirring about 600 parts of a hypochlorous acid solution. Tests with potassium iodide solution showed that excess hypochlorous acid had been added. The reaction mixture was treated with salt. An oil separated and was removed. It was dried over sodium sulfate and distilled. A fraction of 12 parts was. obtained at -81 C./1920 mm. which had a refractive index of 1.4454 and was ethyl a,a-dichloromalonaldehydate.

The compounds of this invention are very versatile chemical intermediates, since they possess three kinds of reactive groups. They react, for example, with amines having available hydrogen. They undergo reactions with hydrazine. The chlorine atoms are replaceable with hydrogen.

We claim:

1. A process for preparing a non-tertiary alkyl a-dichloromalonaldehydate which comprises reacting an alkyl p-alkoxyacrylate in which the alkyl group contains not over four carbon atoms with a dilute solution of hypochlorous acid at a temperature between -5 C. and 20 C.

2. The process of claim 1 in which the alkyl fl-alkoxyacrylate is ethyl p-ethoxyacrylate.

3. The process of claim 1 in which the alkyl fl-alkoxyacrylate is methyl p-methoxyacrylate.

4. The process of claim 1 in which the alkyl fl-alkoxyacrylate is butyl B-butoxyacrylate.

The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Faith Aug. 13, 1946 Number 

1. A PROCESS FOR PREPARING A NON-TERTIARY ALKYL A,A-DICHLOROMALONALDEHYDATE WHICH COMPRISES REACTING AN ALKYL B-ALKOXYACRYLATE IN WHICH THE ALKYL GROUP CONTAINS NOT OVER FOUR CARBON ATOMS WITH A DILUTE SOLUTION OF HYPOCHLOROUS ACID AT A TEMPERATURE BETWEEN -5* C. AND 20* C. 